fix(route53): warn when ttl is provided with alias target

When creating a Route53 RecordSet with an alias target, the ttl property is ignored since alias targets don't use TTL values. This change adds a warning annotation to inform users when they provide a ttl value that will be ignored.
This improves developer experience by making it clear when a provided configuration option has no effect, helping users avoid confusion and potential misconfigurations.

Author: gasolima

packages/aws-cdk-lib/aws-route53/lib/record-set.ts

@@ -7,7 +7,7 @@ import { IHostedZone } from './hosted-zone-ref';
 import { CfnRecordSet } from './route53.generated';
 import { determineFullyQualifiedDomainName } from './util';
 import * as iam from '../../aws-iam';
-import { CustomResource, Duration, IResource, Names, RemovalPolicy, Resource, Token } from '../../core';
+import { Annotations, CustomResource, Duration, IResource, Names, RemovalPolicy, Resource, Token } from '../../core';
 import { ValidationError } from '../../core/lib/errors';
 import { addConstructMetadata } from '../../core/lib/metadata-resource';
 import { propertyInjectable } from '../../core/lib/prop-injectable';
@@ -389,6 +389,9 @@ export class RecordSet extends Resource implements IRecordSet {
     this.multiValueAnswer = props.multiValueAnswer;
 
     const ttl = props.target.aliasTarget ? undefined : ((props.ttl && props.ttl.toSeconds()) ?? 1800).toString();
+    if (props.target.aliasTarget && props.ttl != undefined) {
+      Annotations.of(this).addWarningV2('aws-cdk-lib/aws-route53:ttlIgnored', 'Ignoring ttl since \'target\' uses an alias target');
+    }
 
     const recordName = determineFullyQualifiedDomainName(props.recordName || props.zone.zoneName, props.zone);